Cobalt-nickel electroplating solution



2.834.72 HCOBALTTNIQKEL ELECTRQPLATING soLuTro s ,He rman c. Scheer, Endicott, and Edward R. York Endwell, N. Y., assignors to International Business Ma- "hines Corpomfibi, New Y N. Y., a corporation of New York w No Drawing. Application December 27, 1956 Serial No. 630,750

6 Claims. (Cl. 204-43) This invention relates to improved electroplating solutions for electroplating cobalt-nickel compositions on a metal base. More particularly, this invention relates to improving plating solutions having a wide workable range of cobalt to nickel metal ion ratio which when containing a special additive agent impart to the electroplate high quality magnetic characteristics suitable for various types of magnetic recording.

It is known that cobalt-nickel plating for magnetic recording purposes may be accomplished from solutions containing suitable concentrations of nickel and cobalt salts, using a plating and deplating cycle for the current supplied to the bath. It is further known that the addition of certain organic compounds, such as aromatic sulfonamides, will improve the quality of the plating. However, these previous plating solutions require relatively close control of the cobalt and nickel ratios, and in the case of many of the organic additives, their use is restricted by limited solubility and susceptibility to chemical breakdown which may contaminate the bath.

It has been found that high quality magnetic plating is possible over a wide range of cobalt to nickel metal ion ratio in the presence of small amounts of addition agents known as inorganic thiocyanates, such as potassium, sodium and ammonium thiocyanates. The amount of addition agent which may be employed may vary from SXlO- grams per liter of solution to 5X10 grams per liter of solution. These addition agents are completely soluble, stable for longer periods of time than most organic agents and are essential for obtaining good quality magnetic properties in a'coating.

It is accordingly an object of the subject invention to provide an improved cobalt-nickel plating solution having an extended range for the ratio of cobalt to nickel.

Another object of this invention is to provide an improved cobalt-nickel plating solution employing only chlorides of cobalt and nickel.

Another object of the invention is to provide an improved cobalt-nickel plating solution employing an inorganic additive which substantially improves the magnetic quality of the plated articles.

A further object of the invention is to provide an improved cobalt-nickel plating solution in which improved magnetic qualities are provided by an additive selected from the class of inorganic thiocyanates.

Still another object of the invention is to provide an improved cobalt-nickel plating solution in which improved magnetic qualities are provided by an additive selected from the class of ammonium, potassium and sodium thiocyanate.

A principal object of the invention is to provide an improved cobalt-nickel plating solution.-

The foregoing objects are attained in this invention by providing a water solution of suitable cobalt and nickel salts, preferably chlorides with a relatively high ratio of cobalt to nickel, a small percentage of boric acid, and and extremely small percentage of a thiocyanate, preferably selected from the class including sodium, potassium and ammonium thiocyanates. During the plati g process, the temperature of the bathis maintained between 6(land 8O degrees C. Alternate plating-and deplating cycles are employed in the mannerknown in ,th 'a'rt. Other objects of the invention will b e p 'ntedout in the following descriptionandjclairns.'

' The following'isan example "of an improved electroplating solution according to the presentjinve tio An "aqueous s'olution' is made up in accordance with the idllowing quantities of technical grade chemicals:

The amount of potassium thiocyanate is obtained by successive dilutions to obtain the concentration desired for addition to the solution.

The material to be plated is immersed in the bath as a cathode, and the usual anode of cobalt, nickel, or an alloy of the two metals is also placed in the bath. The plating current is supplied in alternate plating and deplating phases, substantially as described in U. S. Patent 2,619,454. For optimum results, the plating bath should be maintained at a temperature in the range from 60 to degrees centigrade.

The thiocyanate additive may vary Within the limits from 5 10- g./l. to 5x10" g./l. Since it is difficult to accurately quantitatively determine the thiocyanate concentration in the solution, it has been found most expeditious to replenish the additive based upon the plating load of the bath, so that, for a known thickness of plating, the additive may be replenished at a given rate per square feet of plated area.

In the example solution provided, the cobaltmickel ratio is 2.87 to 1, by analysis. However, it has been found that by the use of the thiocyanate additives it is possible to obtain plating having the desired magnetic qualities with the cobaltznickel ratio varying anywhere in the range from 2.25/1 to 2.9/1.

As previously noted, sodium and ammonium thiocyanates are known to function equally as well as potassium thiocyanate, within the limits given above.

While there have been shown and described and pointed out the fundamental novel features of the invention as applied to a preferred embodiment, it will be understood that various omissions and substitutions and changes in the form and details thereof may be made by those skilled in the art, Without departing from the spirit of the invention. It is the intention, therefore, to be limited only as indicated by the scope of the following claims.

What is claimed is:

1. An electroplating solution for depositing a coating of an alloy consisting of cobalt and nickel, which consists of a water solution containing chlorides of cobalt and nickel, boric acid, and a thiocyanate from the class consisting of sodium, potassium and ammonium thiocyanates, the amount of thiocyanate ranging from 5 10 to 5x10 grams per liter. 1

2. An electroplating solution for depositing a coating of an alloy consisting of cobalt and nickel, which consists of a water solution containing chlorides of cobalt and nickel, boric acid, and sodium thiocyanate, the amount of thiocyanate ranging from 5x10- to 5X10- grams per liter.

3. An electroplating solution for depositing a coating of an alloy consisting of cobalt and nickel, which consists of a water solution containing chlorides of the metals of said class, boric acid, and potassium thiocyanate,

3 the amount of thiocyanate ranging from 5X10- to 5 10- grams per liter.

4. An electroplating solution for depositing a coating of an alloy consisting of cobalt and nickel, which consists of a water solution containing chlorides of the metals of said class, boric acid, and ammonium thiocyanate, the amount of thiocyanate ranging from 5x10- to 5x10- grams per liter.

5. A cobalt-nickel plating solution consisting of an aqueous vehicle in which have been dissolved nickel and cobalt salts so that the ratio of cobalt to nickel content is from 2.25/1 to 2.9/1 and in which have been dissolved boric acid in the amount of 5 to 40 grams per liter and between 5 10- and 5 X 10- grams per liter of a thiocyanate taken from the class consisting of sodium, potassium and ammonium thiocyanates.

6. A cobalt-nickel plating solution consisting of an aqueous vehicle in which have been dissolved nickel and cobaltous chlorides so that the ratio of cobalt to nickel content is from 2.25/1 to 2.9/1, boric acid in the amount of 5 to 40 grams per liter and between 5X10- and 5 x 10- grams per liter of a thiocyanate taken from the class consisting of sodium, potassium and ammonium thiocyanate.

No references cited.

U. S. DEPARTMENT OF COMMERCE PATENT OFFICE CERTIFICATE OF CORRECTION Patent No, 2,8349'725 Herman G a Seheer 'et al, May 13, 1958 It is hereby certified that error appears .in the printed specification 4 of the above numbered patent requiring correction and that the said Lettere Patent should read as corrected below.

Column 2 lines 71 and 72 and column 3, lines 5 and 6, for "the metals of said class"; each 0eenrrenc'c-z v read cobalt and nickel Signed and sealed. this 29th day of July 1958.a

(SEAL) Attest:

KARI. H AXL ,1

INF ROBERT c. WATSON Attesting Officer Conmissioner of Patents 

1. AN ELECTROPLATING SOLUTION FOR DEPOSITING A COATING OF AN ALLOY CONSISTING OF COBALT AND NICKEL, WHICH CONSISTS OF A WATER SOLUTION CONTAINING CHLORIDES OF COBALT AND NICKEL, BORIC ACID, AND THIOCYANATE FROM THE CLASS CONSISTING OF SODIUM, POTASIUM AND AMMONIUM THIOCYANATES, THE AMOUNT OF THIOCYANATE RANGING FROM 5X10-4 TO 5X10-3 GRAMS PER LITER. 